1. Field of the Invention
The present invention relates to medical and surgical tubes, and more particularly relates to cannulae and venous cannula and the like, as used in cardio-pulmonary bypass operations. Even more particularly the present invention relates to a venous cannula apparatus and its method of installation wherein a single cannula structure mounted in a single opening with a purse string, for example, closure provides branch tube members forming fluid connections with the superior and inferior vena cava.
2. General Background and Prior Art
When a surgeon places a patient on a cardio-pulmonary bypass machine, there is required a fluid connection between the heart and the machine. The machine circulates both blood returning from the body to the heart, termed the venous return, and blood pumped into the body from the heart-lung machine, termed the arterial outflow. The venous return is normally collected by a flexible tube, or several flexible tubes which is/are known in the art as a cannula(e) or venous cannula(e). The cannula is fed through an opening in the artium which opening is formed by the surgeon. The surgeon provides a "purse string" suture for example to seal the cannula properly after it is placed through the opening. The lower portion of the ell-shaped cannula is inserted in a curved fashion into the superior or inferior vene cava.
Presently, two tubes are usually required since each must make an approximate ninety degree bend for its proper placement and operation. The placement of a "tee" or "wye" would not be possible since such a structure could not pass through a small purse string opening. Due to the desire to reduce trauma to the heart, two very small openings are thus made with a single substantially ell-shaped cannula being entered and placed through each respective surgical opening, one tube or cannula placed through the atrium to the inferior vena cava, the other being placed through a second respective opening into the superior vena cava.
After placement of the cannulae a substantially fluid tight seal is formed using the purse string suture about the surgical opening by utilizing snares or clamps around the inferior vena cava and superior vena cava to form fluid tight connections with the cannula tube and the respective vein.
The placement aforedescribed of two separate cannula structures still represents a serious trauma to the heart with two surgical openings being formed. The operative procedure of placing two cannulae in the atrium and superior and inferior vena cava consumes a significant amount of time.
3. General Description of the Present Invention
The present invention solves all the prior art problems and shortcomings in a simple and inexpensive manner. The present invention provides a cannula structure which is comprised of an upper fluid conveying tube having preferably two lower branch tube members which are normally urged to an angular tee-like position with respect to the upper tube portion of the cannula.
An outer slideable sleeve is fitted over the upper tube structure and slides up and down the cannula with respect to its central bore. The sleeve is substantially stiff and its movement along the upper tube to the lower tube branches urges the tube branch members into a substantial alignment with the upper fluid conveying tube. Thus, the sleeve urges the branch members of the cannula into an aligned "collapsed" position so the entire structure can be passed through a single suture opening as is desirable. The combined external diameter of the two tube branch members is substantially equal to the external diameter of the main fluid conveying tube. The outer sleeve provides an internal diameter slightly greater than the external diameter of the main fluid conveying tube. Thus a slideable fit is achieved (Note FIGS. 1 and 2). The sleeve then provides the maximum diameter of the cannula structure in its "collapsed" state which allows placement of the structure through a minimal diameter opening in the atrium (See FIG. 4A).
After placement of the lowermost portion of the aligned tube branch members through the single surgical opening, the surgeon can slowly remove the sleeve in an upward fashion with the two branch tubes (now inside the atrium) being urged by "memory" into their proper angular "operative" positions feeding the inferior and superior vena cava respectively. Clamps secure the branch tubes in these operative positions (See FIG. 4C).
Memory can be supplied to the branch members by utilizing a suitable plastic-like material which will cause each branch member to spring back into its tee-like orientation when the outer sleeve is removed.